Phosphate treatment is to put metal into a solution containing phosphate for chemical treatment, so that a phosphate protective film that is insoluble in water and has good adhesion is formed on the surface of the metal, that is, a phosphate film.
As a primer for paint and as an adsorption layer for lubricants during cold working of metals. Since the phosphate film is composed of a series of crystals of zinc, manganese, iron hydrogen phosphate and phosphate of different sizes, the film is porous, has a large surface area, and has good adsorption properties, which can absorb paint or paint. A large amount of lubricant, so it is often used as the bottom layer of paint, or as a lubricating layer for cold stamping to reduce friction and cold drawing of steel pipes and steel wires.
Phosphate film is insoluble in water, very stable in the atmosphere, and can be used as a protective layer with low anti-rust requirements. If the phosphate film is sealed with a chromate film, immersed in oil or painted, its corrosion resistance ability can be further improved.
The protective system composed of phosphate film and nitro paint or synthetic resin paint has a very good anti-corrosion effect on steel. When the paint is prepared, the viscosity should be so that the paint can freely penetrate the film pores. The drying temperature of the paint film should be suitable. Between 150~180 ℃, it is best to dry in an oven.
When the phosphate film is used for cold deformation processing and to reduce the surface wear of friction parts, immersing the film with oil or soap lubricants can improve its use effect. The most convenient and effective method is to immerse it in potassium soap solution.
The most widely used phosphate films are iron phosphate film, zinc phosphate film and manganese phosphate film. Among them, zinc phosphate film and manganese phosphate film are not oxidized by oxygen in the atmosphere and have better corrosion resistance.
